<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>Chapter9</title>
    <style>
        html,
        body {
            height: 100%;
        }
        
        body {
            margin: 0;
            padding: 0;
            font-size: 18px;
            font-weight: bold;
        }
        
        header {
            margin: 5px;
            height: 60px;
            border: 2px solid #000;
            clear: both;
        }
        
        nav {
            margin: 5px;
            border: 2px solid #000;
        }
        
        #sidebar {
            margin: 5px;
            min-height: 600px;
            float: left;
            width: 20%;
            border: 2px solid #000;
        }
        
        #content {
            margin: 5px;
            min-height: 600px;
            float: right;
            width: 70%;
            border: 2px solid #000;
        }
        
        footer {
            clear: both;
            height: 30px;
            border: 2px solid #000;
        }
    </style>
</head>

<body>
    <header>
        header
    </header>
    <nav>
        nav
    </nav>
    <div id="sidebar">
        sidebar
    </div>
    <div id="content">
        content
    </div>
    <footer>
        footer
    </footer>
</body>

</html>